Caught a Ring...Major Damage. Q's.

[keithb7]

I own a 93 CR265 and on sunday had a massive failure. Bottom piston ring bound up on the upper exh port, tore up the port pretty bad, piston is thrashed, as well the head looks like it has been through a blender. I checked and the locating dowel in the piston ring groove is still in place, so it appears that the ring did not turn. I put new piston rings in about 1.5 mos ago, and rode it about 4 times since then. Everything was great until Sunday past. What are some of the reasons a ring would catch on exh port? Assuming rings are correct size, proper oil mixture and jetting, cylinder is nikasil coated. Could poor warm up cause this? I run a wiseco piston, and before the failure allowed the bike to warm up for about a minute. It was not cold, I had rode it hard about an hour earlier.

Question 2: There are pieces of piston ring down in the bottom under the crank. Is there a way to get them out without splitting the cases? Remove the engine turn it over and blast in some varsol?

Thanks, Keith

 

[ZOMBIE666]

cant help much with Q#1 but with Q#2, I would definitely tear it apart, if its as bad as it sounds, there could be all kinds of little pieces of junk stuck places u cant see. Why spend all the cash on replacing the piston, rings and so on just to have it blow up again from a tiny chunk of ring you missed while cleaning her out. Just my 2 cents

 

[darringer]

I had a similar problem with my 265. I think it was running a bit lean and ran hot. The exhaust bridge is the hottest part of the cylinder. Could have possibly stuck a ring on the bridge as mine did. After sending the topend back to Eric Gorr, he drilled three holes in the Wiseco piston where the exhaust bridge is. He said it would help keep the bridge cooler, but spooge a bit more. He explained that the Wiseco pistons are relieved at the port and don't normally need the holes drilled, but it gives added cooling. I have a few long rides on the bike since and it runs excellent with zero problems.

As far as flushing the lower end out, you can use old premix to flush. Just be certain to get all of the little pieces out.

 

[Pete Payne]

Sounds like time to go to the 69.5mm piston ....

 

[Fultoncm]

My piston hit my exhaust valve because the exhaust valve broke off the arm and slid down about 1/16" into the cylinder. Did the exhaust valve break apart?

Also, the Wiseco I just bought had a piece of red paper with instructions that some bikes needed exhaust bridge holes drilled in them. You may have needed to do this with your set up.

 

[keithb7]

I rode the bike a full year with no problems, without drilling any addidtional holes. It ran flawlessly for a year with lots and lots of riding time. In Feb. all I did was change the rings, re-used the wiseco piston.
I am reluctant to split the case but maybe I better, will decide. In the mean time I bought a brand new 2006 RM-Z450 2 days ago. It will be the main steed now, the 1993 CR was getting pretty old anyway. I'll fix it up and decide what to do with it. I may keep it as a 2-stroke is a lot of fun, then I have options.

 

[darringer]

I had never drilled the holes with previous rebuilds on my 99cr250 and also on two different '02s with the standard bore. According to Eric, it was unnecessary. Running my jetting on the lean side was probably the cause in my instance. With the overbore, Eric clearances the bridge even further, but decided to drill the holes for extra protection. I will continue this practice also. Your circustance is quite different, with a mechanical failure of the exhaust valve causing the damage.

 

[Pete Payne]

Drilling the holes are for a bridged exhaust port . That would be the 2002 thru 2006 CR250 . 2001 and earlier models do not require this .